Remove foreign language audio and subtitle tracks from mkv files in bulk

removeNonEnglish.py

#!/usr/bin/python

# Removes non-LANG audio tracks and subtitles from mkv files in a directory.
# Original script by greenbender at https://forum.videohelp.com/threads/343271-BULK-remove-non-English-tracks-from-MKV-container
# Modified by Joseph Milazzo for updated MkvMerge commands.
# 12/3/2021: Updated to Python 3.9

import os
import re
import sys
import subprocess
import json

# change this for other languages (3 character code)
LANG = "eng"

# set this to the path for mkvmerge
MKVMERGE = "mkvmerge.exe"

AUDIO_RE = re.compile(
    r"Track ID (\d+): audio \([A-Z0-9_/]+\) [number:\d+ uid:\d+ codec_id:[A-Z0-9_/]+ codec_private_length:\d+ language:([a-z]{3})")
SUBTITLE_RE = re.compile(
    r"Track ID (\d+): subtitles \([A-Z0-9_/]+\) [number:\d+ uid:\d+ codec_id:[A-Z0-9_/]+ codec_private_length:\d+ language:([a-z]{3})(?: track_name:\w*)? default_track:[01]{1} forced_track:([01]{1})")

if len(sys.argv) < 2:
    print("Please supply an input directory")
    sys.exit()

in_dir = sys.argv[1]

for root, dirs, files in os.walk(in_dir):
    for f in files:

        # filter out non mkv files
        if not f.endswith(".mkv"):
            continue

        # path to file
        path = os.path.join(root, f)

        # build command line
        cmd = [MKVMERGE, "-J", path]

        # get mkv info
        mkvmerge = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        stdout, stderr = mkvmerge.communicate()
        if mkvmerge.returncode != 0:
            print >> sys.stderr, "mkvmerge failed to identify", path
            continue

        # find audio and subtitle tracks
        audio = []
        subtitle = []
        info_json = json.loads(stdout)
        tracks = info_json['tracks']
        for track in tracks:
            track['properties']['id'] = track['id']
            if track['type'] == 'audio':
                audio.append(track)
            elif track['type'] == 'subtitles':
                subtitle.append(track)

        # filter out files that don't need processing
        if len(audio) < 2 and len(subtitle) < 2:
            print >> sys.stderr, "nothing to do for", path
            continue

        # filter out tracks that don't match the language
        audio_lang = filter(lambda a: a['properties']['language'] == LANG, audio)
        subtitle_lang = filter(lambda a: a['properties']['language'] == LANG, subtitle)

        # filter out files that don't need processing
        if len(audio_lang) == 0 and len(subtitle_lang) == 0:
            print >> sys.stderr, "no tracks with that language in", path
            continue

        # build command line
        cmd = [MKVMERGE, "-o", path + ".temp"]
        if len(audio_lang):
            cmd += ["--audio-tracks", ",".join([str(a['id']) for a in audio_lang])]
            for i in range(len(audio_lang)):
                cmd += ["--default-track", ":".join([str(audio_lang[i]['id']), "0" if i else "1"])]
        if len(subtitle_lang):
            cmd += ["--subtitle-tracks", ",".join([str(s['id']) for s in subtitle_lang])]
            for i in range(len(subtitle_lang)):
                cmd += ["--default-track", ":".join([str(subtitle_lang[i]['id']), "0"])]
        cmd += [path]

        # process file
        print >> sys.stderr, "Processing", path, "...",
        mkvmerge = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        stdout, stderr = mkvmerge.communicate()
        if mkvmerge.returncode != 0:
            print >> sys.stderr, "Failed"
            print(stdout)
            continue

        print >> sys.stderr, "Succeeded"

        # overwrite file
        os.remove(path)  # Don't overwrite
        os.rename(path + ".temp", path)

Unfortunately it does not work on python 3.11

  File "script.py", line 73, in <module>
    if len(audio_lang) == 0 and len(subtitle_lang) == 0:
       ^^^^^^^^^^^^^^^
TypeError: object of type 'filter' has no len()

Hey,
It doesn't seem to work, os.walk(in_dir): seems to return nothing, all my mkv files are in 'Z:\Season 1' folder
But the program doesn't find any files

It seems it is a problem if the files are on a network drive

Hey, It doesn't seem to work, os.walk(in_dir): seems to return nothing, all my mkv files are in 'Z:\Season 1' folder But the program doesn't find any files

It seems it is a problem if the files are on a network drive

There are a lot of issues in general when working across operating systems and file systems over the network.

I spent hours one time trying to debug something and I was running Python on Windows but accessing files on a Linux shared drive. Windows is not case sensitive and linux is and it was a huge learning moment for me.

I would encourage you to try running the script on the same platform as your network drive or dig further into the exact file systems you're running on both devices and why you might be seeing an issue that you are.